How soon will you see her in person? Because I think face to face is the way to go.
Though regardless of whether or not it's face to face, start out by asking "how are you doing?" and listen to her answer. If you're not sure how to act after she tells you, then ASK her what she needs from you. She's really the only one who can tell you what she needs.
Most of all though, the next move is about listening to her and letting her tell you what she needs now. It's not a time for you to express regrets or make it about you.
Never regret anything that has happened in your life. It cannot be changed, forgotten or undone. So, take it as a lesson learned and move on.